If abuses are destroyed, man must destroy them. If slaves are freed, man must free them. If new truths are discovered, man must discover them. If the naked are clothed; if the hungry are fed; if justice is done; if labor is rewarded; if superstition is driven from the mind; if the defenceless are protected and if the right finally triumphs, all must be the work of man. The grand victories of the future must be won by man, and by man alone.

Robert Green Ingersoll (1833-1899) American lawyer, freethinker, orator

Lecture (1872-01-29), “The Gods,” Fairbury Hall, Fairbury, Illinois
    (Source)

On not waiting for divine intervention to solve social ills.

First given on the 135th birthday of Thomas Paine. Collected in The Gods and Other Lectures (1876).